Add user into sudoers file, to give superuser permissions in debian wheezy

If you are getting an error message like this " is not in the sudoers file. This incident will be reported." when using commands with sudo in debian wheezy.
You can solve this by editing the /etc/sudoers file.

Login as root then
vim /etc/sudoers

then find out the line
root    ALL=(ALL:ALL) ALL

copy paste the line again in the next line and change the root into your username.
arun   ALL=(ALL:ALL) ALL
My username is 'arun'.

Then save it. Use :qw! to force saving the file.
That is it, now exit from root and try sudo ls, or sudo any command.